mirror of
https://github.com/coredns/coredns.git
synced 2025-11-04 03:03:14 -05:00
103 lines
3.4 KiB
Go
103 lines
3.4 KiB
Go
package core
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import (
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"bytes"
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"fmt"
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"io/ioutil"
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"log"
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"os"
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"os/exec"
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"runtime"
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"strconv"
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"strings"
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"sync"
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)
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// isLocalhost returns true if host looks explicitly like a localhost address.
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func isLocalhost(host string) bool {
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return host == "localhost" || host == "::1" || strings.HasPrefix(host, "127.")
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}
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// checkFdlimit issues a warning if the OS max file descriptors is below a recommended minimum.
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func checkFdlimit() {
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const min = 4096
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// Warn if ulimit is too low for production sites
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if runtime.GOOS == "linux" || runtime.GOOS == "darwin" {
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out, err := exec.Command("sh", "-c", "ulimit -n").Output() // use sh because ulimit isn't in Linux $PATH
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if err == nil {
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// Note that an error here need not be reported
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lim, err := strconv.Atoi(string(bytes.TrimSpace(out)))
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if err == nil && lim < min {
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fmt.Printf("Warning: File descriptor limit %d is too low for production sites. At least %d is recommended. Set with \"ulimit -n %d\".\n", lim, min, min)
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}
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}
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}
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}
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// signalSuccessToParent tells the parent our status using pipe at index 3.
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// If this process is not a restart, this function does nothing.
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// Calling this function once this process has successfully initialized
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// is vital so that the parent process can unblock and kill itself.
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// This function is idempotent; it executes at most once per process.
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func signalSuccessToParent() {
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signalParentOnce.Do(func() {
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if IsRestart() {
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ppipe := os.NewFile(3, "") // parent is reading from pipe at index 3
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_, err := ppipe.Write([]byte("success")) // we must send some bytes to the parent
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if err != nil {
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log.Printf("[ERROR] Communicating successful init to parent: %v", err)
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}
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ppipe.Close()
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}
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})
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}
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// signalParentOnce is used to make sure that the parent is only
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// signaled once; doing so more than once breaks whatever socket is
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// at fd 4 (the reason for this is still unclear - to reproduce,
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// call Stop() and Start() in succession at least once after a
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// restart, then try loading first host of Caddyfile in the browser).
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// Do not use this directly - call signalSuccessToParent instead.
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var signalParentOnce sync.Once
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// caddyfileGob maps bind address to index of the file descriptor
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// in the Files array passed to the child process. It also contains
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// the caddyfile contents and other state needed by the new process.
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// Used only during graceful restarts where a new process is spawned.
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type caddyfileGob struct {
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ListenerFds map[string]uintptr
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Caddyfile Input
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OnDemandTLSCertsIssued int32
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}
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// IsRestart returns whether this process is, according
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// to env variables, a fork as part of a graceful restart.
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func IsRestart() bool {
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return os.Getenv("CADDY_RESTART") == "true"
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}
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// writePidFile writes the process ID to the file at PidFile, if specified.
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func writePidFile() error {
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pid := []byte(strconv.Itoa(os.Getpid()) + "\n")
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return ioutil.WriteFile(PidFile, pid, 0644)
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}
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// CaddyfileInput represents a Caddyfile as input
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// and is simply a convenient way to implement
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// the Input interface.
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type CaddyfileInput struct {
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Filepath string
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Contents []byte
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RealFile bool
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}
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// Body returns c.Contents.
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func (c CaddyfileInput) Body() []byte { return c.Contents }
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// Path returns c.Filepath.
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func (c CaddyfileInput) Path() string { return c.Filepath }
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// IsFile returns true if the original input was a real file on the file system.
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func (c CaddyfileInput) IsFile() bool { return c.RealFile }
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